This application is related to my copending patent application Ser. No. 822,529, filed Jan. 27, 1986.
1. Field of the Invention
This invention relates to a new process for particle fractionation. More particularly, the invention relates to a new process for fractionation of particulate or molecular components and/or concentration or purification of said components according to size or to other physical characteristics, and to a new type of apparatus for accomplishing the same.
Specifically, the invention provides a new continuous and rapid process for separation of particulate or molecular components which have different equilibrium positions or distributions across the thickness of a thin channel. The new process broadly comprises introducing a stream of fluid containing the particulate or molecular components to be separated or concentrated into the inlet end of a thin enclosed channel whose transverse dimension is very small, preferably much smaller than the other two dimensions, applying a special field or gradient or combination thereof transversely across the thin dimension of the channel to create a driving force a component of which is perpendicular to the main flow plane, adjusting the flow rate to achieve laminar flow conditions throughout the channel or at least throughout a sufficient portion of the channel immediately preceding the outlet end to allow the particulate or molecular components under the influence of the field/gradient to wholly or partially segregate into different stream laminae as they approach different transverse equilibrium positions, splitting the channel stream at the outlet end into substreams containing different separated purified or concentrated fractions of the particulate or molecular components in the sample mixture, recovering the substream and thereby recovering the separated or concentrated fractions of the initial mixture.
As a special embodiment, the invention further provides a process for separating or concentrating particulate or molecular components using at least one of the above-described thin channels linked to one or more additional channels of the same or different type wherein the channels are joined by fluid streams in which one or more of the outlet streams from one or more channels is fed to the inlet stream of one or more other channels.
The invention further provides a new type of separation apparatus for use in the above-noted process which comprises one or more special thin channels or cells which permits one to effect the above-noted rapid and efficient separation of the particulate or molecular components.
2. Prior Art
There is a growing need in industry for the separation of particles including both cell-size particles and those of submicron and macromolecular size, such as various viruses, latices and polymers. Various methods have been proposed, but in general, they have been too slow, too low in throughput, too complicated, inefficient, expensive or have failed to effect the separation with the desired degree of resolution needed for commercial operations.
Some of the best techniques disclosed have been those based on field-flow fractionation as disclosed in U.S. Pat. Nos. 3,449,938, 4,147,621 and 4,250,026. Other references include Giddings, Anal. Chem. 57945 (1985), and Giddings et al Sep. Science and Tech. 18 (3) 293-306 (1983). These prior known methods, however, are limited in throughput as they are batch techniques that do not operate normally on a continuous basis. They are designed as analytical-scale techniques and they fail to resolve adequate quantities of material needed for many applications.
It is an object of the invention, therefore, to provide a new and efficient process for the fractionation of particulate or molecular components and/or the concentration or purification of such components. It is a further object to provide a new process for fractionation of particles based on the different equilibrium positions or distributions they assume across the thickness of a thin channel when subject to special driving forces. It is a further object to provide a new process for the separation of particles from fluid media which can be accomplished in a rapid and efficient manner. It is a further object to provide a new process for particle fractionation which permits good resolution of separation. It is a further object to provide a process for separation of particles from fluid media which can be operated in a continuous manner. It is a further object to provide a new process for particle fractionation which permits separation on a single pass through the apparatus. It is a further object to provide a new separation process which is economical to operate and uses inexpensive equipment. It is a further object to provide a new type of apparatus for the separation of particles which can be operated singly or in combination with other types of separation equipment. These and other objects will be apparent from the following detailed description thereof.